With the rapid and strong development of large interconnection networks, such as Internet, route technology more and more becomes a key of network technology and routers become one of greatly important network devices. By using the routers, the networks can be interconnected and isolated.
In a data communication network including a plurality of routers, when the router receives data packets and routes them, its operations comprise two actions: finding a pathway (routing selection) and forwarding data packets. Finding the pathway comprises determining an optimal pathway to a destination, which can be implemented with a routing selection algorithm. To find the optimal pathway, it is necessary to establish a routing table including routing information. According to the routing table, the router can know relationships between the destination and a next-hop router and determine the optimal pathway based on measurements. Forwarding data packets comprises transmitting the data packets along the optimal pathway. When receiving the data packets, the router searches the routing table based on the information in the packet head to determine the next-hop router and then transmits the data packets to the next-hop router. Through the above operations, the data packets can be transmitted in the network.
FIG. 1 is a schematic diagram showing the data communication network system including seven routers R1-R7 is changed. As shown in FIG. 1, there are two pathways from a source router R1 to a destination router R7: R1→R2→R3→R7 and R1→R4→R5→R6→R7, wherein the optimal pathway is R1→R2→R3→R7. In this way, when transmitting the data packets, the source router R1 selects the router R2 as the next-hop router and transmits the data packets to the router R2. Then, the router R2 selects the router R3 as the next-hop router and transmits the data packets to the router R3. Finally, the router R3 transmits the received data packets to the destination router R7. However, if the router R2 is removed or down, or the bandwidth of the router R2 becomes small, for example, from 1 Gbps to 1 Mbps, the overall performance of the pathway R1→R2→R3→R7 will be limited by the performance of the segment R2→R3 which will adversely influence the transmission of the data packets or cause the quality of service of the transmission pathway to be decreased.